Catalytic carbonylation of epoxides, aziridines, thiiranes, oxetanes, lactones, lactams and analogous compounds have been shown to be useful for the synthesis of ring expanded products of such compounds. The early catalyst for the carbonylation of epoxides was based on the use of [Co2(CO)8]. EP-B-0 577 206 by Drent and Kragtwijk relates to a process for the carbonylation of epoxides to form beta-lactone in the presence of [Co2(CO)8] and a hydroxy substituted pyridine compound. Alper and co-workers (J. Org. Chem. 2001, 66, 5424-5426) reported increased activity of carbonylation and selectivity for beta-lactone using combinations of [PPN]+[Co(CO)4]− and neutral metal complexes (PPN=bis(triphenylphosphine)iminium).
Further improvement of activity of carbonylation disclosed in U.S. Pat. No. 6,852,865 relates to bimetallic catalysts of the general type [metal complex]+[Co(CO)4]− for the ring-expanding carbonylation of epoxides, aziridines, thiiranes, oxetanes, lactones, lactams and analogous compounds.
Nonetheless, there remains a need for catalysts that have increased activity that will further reduce the catalyst cost in the carbonylation of epoxides, aziridines, thiiranes, oxetanes, lactones, lactams and analogous compounds.